Carburetor choking device



Jan. 2, 1968 D. F. MORGAN ET AL 3,361,416

CARBURETOR CHOKING DEVICE 2 Sheets-Sheet 1 Filed July 18, 1966 I v/ 2:2 U I ll I I 70 a0 zz U I /16 if 68 2'8 1% y,-

o0 ALVVENTOR WITNESS: W i f m ATTORNEY Jan. 2, 1968 F. MORGAN ET CARBURETOR CHOKING DEVICE Filed July 18, 1966 M/XTURE RH 770 WITNESS I 2 SheetsSheet 2 FAST IDLE A/R FLOW FUR FLOW INVENTOR.

ATTOBZVE T United States Patent C 3,361,416 CARBURETOR CHOKING DEVICE Donald F. Morgan, Horseheads, and Albert H. Winkler, Elmira, N.Y., assignors to The Bendix Corporation, a corporation of Delaware Filed July 18, 1966, Ser. No. 565,930 4 Claims. (Cl. 26139) ABSTRACT OF THE DISCLOSURE An improved cold engine enrichment arrangement for carburetors essentially using components now present in existing carburetors, but altering the interrelationship between components to produce an improved cold engine operating characteristic. More specifically, a power jet enrichment device, normally used for high speed and power enrichment, is altered by relocating its actuating vacuum pick-up point in relation to a throttle valve such that the power jet is also cut in and provides enrichment at cold or fast idle settings. Supplementing this, an automatic choke system is designed to provide less enrichment than would be the case were it solely responsible for cold engine enrichment. By utilizing the choke and power jet in combination, a better operating characteristic is obtained that leads to economy of fuel without appreciably increasing the cost of a carburetor.

Commonly, prior art carburetors have automatic choking devices using bimetal thermostats and vacuum motors to control the position of the choke valve. Such conventional automatic choke type carburetors, in providing a rich fuel-air mixture for satisfactory cold engine idle operation, provide a fuel-air mixture too rich for economical engine operation at speeds above cold engine idle speed prior to warm up and when operating above a predetermined manifold vacuum.

It is an object of the present invention to enrich cold engine fuel-air mixture at cold engine idle speed and to lean out cold engine fuel-air mixture at engine speeds above cold engine idle speed when operating above a predetermined manifold vacuum.

It is an object of the present invention to improve cold engine fuel economy.

It is an object of the present invention to provide an inexpensive, reliable carburetor choking device which may be incorporated into existing carburetor designs.

It is a further object of the present invention to pro vide an improved carburetor choking device which regulates fuel-air mixture by modifying the conventional operation of some of the elements in the carburetor metering system that meters fuel to the engine rather than merely regulating the air flow through the carburetor.

It is a further object of the present invention to provide an off-idle fuel-air mixture enrichment device.

Other objects and advantages will be apparent from the description which follows, taken in conjunction with the accompanying drawing of an embodiment of the invention in which:

FIGURE 1 is a sectional view of a carburetor;

FIGURE 2 is a fragmentary sectional view of an embodiment of the present invention showing it in fuel-air mixture enriching operation;

FIGURE 3 is a fragmentary sectional view of a second embodiment of the present invention showing it in a fuelair mixture enriching position; and

FIGURE 4 is a graph showin the performance characteristics of an embodiment of the present invention.

Turning now to FIGURE 1, numeral 10 indicates generally a carburetor having an air horn 12, main body 14, throttle body 16 and a fuel-air induction passage 18. Fuel Patented Jan. 2, 1968 is supplied to the fuel chamber 20 by any suitable means through a fuel inlet 22 which is opened or obstructed in accordance with the needle valve 23 position which is controlled by the float 24 in the conventional manner.

Fuel for warm engine idle operation is supplied through the conventional idle system. The conventional idle system comprises idle fuel discharge holes 26, a primary idle air bleed 28, an idle tube 30 with a metering orifice 32, a secondary idle air bleed 34 and an idle needle valve 36.

The primary fuel metering and discharge system includes a main metering jet 38, a main discharge jet 4i) and a main jet plug 42 which, in part, defines a main or primary fuel path 44. Air is supplied through the high speed bleeders 56 by the high speed bleeder dome 48. The fuel-air mixture is discharged into the fuel-air passage through the auxiliary or secondary venturi tube 49.

The conventional carburetor design also generally includes a power system or auxiliary fuel supply system to provide a richer mixture for maximum power and high speed operation. The auxiliary system or power system includes a power by-pass jet or valve 50 which has a valve stem 52, a valve body 54 and a valve spring 56. When the power by-pass jet is in the position shown in FIGURE 1, fuel flows through the jet channel 58, past the valve body 54 and into a power fuel supply channel or auxiliary channel 68 feeding into the main discharge tube 40. The power or auxiliary system is controlled by a vacuum motor which has a vacuum piston 62. The lower section of the piston is vented by a bleed 64 to substantially atmospheric pressure upstream in the passage 18. The top of the piston (as shown in FIGURE 1) is maintained at pressure downstream in the passage 13 by a duct or manifold vacuum channel 66 which has an outlet 68 (best shown in FIGURE 2) upstream of the throttle valve 76 and downstream of the choke shaft 72 and choke valve 74 when the throttle valve is in the idle and fast idle positions. As the throttle valve 76 is opened beyond the fast idle position, the edge of the valve 78 passes over the vacuum channel opening 68 and exposes it to the manifold vacuum on the downstream side of the throttle valve 76. In this mode of engine operation, manifold vacuum is communicated to the top of the vacuum motor piston 62 and is sufficient to overrule the compression spring 81 and hold the vacuum piston 62 in the up position as shown by the dotted line in FIGURE 1. In the up position, the power or auxiliary fuel supply system is closed or inoperative and no additional fuel is being supplied to the main discharge tube at through the auxiliary channel 69.

Conventional automatic choke carburetors typically have a bimetal thermostat element and a vacuum motor which regulate and control the position of the offset choke valve and a fast idle control mechanism which opens or positions the throttle valve in the cold engine idle position or fast idle position substantially as shown in solid lines in FIGURES 1 and 2. These wellknown mechanisms are shown, for example, in US. Patent 2,420,917, issued to Sutton and Winkler.

The present invention resides in the novel construction, combination and arrangement of parts as will be described in detail. Prior art carburetors utilized various methods of controlling the choke valve position to obtain the desired cold engine fuel richness at cold engine idle or fast idle, and then relied on air flow forces on the unbalanced or offset choke valve to lean out the fuel-air mixture above the cold engine fast idle speed range. The present invention utilizes the power or auxiliary fuel supply system for added cold engine fast idle enrichment. This permits setting the conventional choke enrichment settings leaner, and yet maintains the required fast idle col-d engine fuel enrichment. The present invention obtains cold engine fuel economy by closing off the auxiliary fuel supply soon after the cold engine fast idle speed range and below the high speed range. This effect is achieved by locating the vacuum channel or duct outlet 68 upstream of the throttle valve 76, and more particularly, upstream of the throttle valve edge 78 when the throttle valve is in the cold engine fast idle speed range. When the cold engine speed is in the fast idle speed range, the throttle valve is in the solid line position shown in FIGURE 2 and prevents manifold vacuum from communicating with the passage 18 and the duct 66. The compression spring 81 is not overruled and the fuel-air mixture is enriched in accordance with engine requirements. \Nhen engine speed exceeds the cold engine fast idle speed range, the throttle is in the more open position shown by the dotted line in FIGURE 2, and the vacuum channel or duct outlet 68 is maintained at the high vacuum existing below the throttle valve. In this position, the auxiliary fuel supply system closes by drawing up the piston 62 against the compression spring 81 and the fuel-air mixture is leaned considerably. Of course, under a substantially wide open throttle valve as shown in phantom in FIGURE 1, the auxiliary power fuel supply system operates in its customary manner. When the channel or duct 66 pressure approaches atmospheric pressure, the compression spring 81 expands to drive the piston 62 downward (as shown in solid in FIGURE 1) and propel the valve stem 52 in an open direction and its bias spring 56 opening the power by-pass jet and enriching the fuel-air mixture ratio.

Turning now to FIGURE 3 wherein is shown a second embodiment of the present invention in which like parts bear the same numeral as they had in FIGURES 1 and 2, except that the sufiix a is added thereto. A first outlet 100 is located in the passage downstream of the throttle valve when it is in an idle position or first position, and upstream of the throttle valve when it is in a fast idle or second position. A channel or duct or chamber 102 interconnects the outlet 100 to the vacuum channel 66a through ball check valve 108. A second oulet 104 is disposed in the passage upstream of the throttle valve when it is in the fast idle and idle position, or in the first and second positions. A channel or conduit 106 interconnects the outlet 134 to the channel 66a. A valve, shown as a one-way ball check valve 108, is disposed in the chamber or conduit 192 to prevent the air in channel 192 from bleeding down the vacuum in channels 106 and 66:: when the vacuum in outlet 104 is higher than in outlet 160. In operation, when the throttle valve edge 7 8a is upstream of the outlet 100 and downstream of the outlet 104, as shown in solid line, the vacuum from the engine is operative to close the power by-pass valve 50, and to prevent the feeding of additional fuel to the engine. When, however, the throttle valve is in the position shown in dotted line designated position x in FIGURE 3, such that the throttle valve edge is downstream of the outlet 109 and downstream of the outlet 104, engine vacuum is not communicated to the power by-pass valve 50 and it is operative to enrich the fuel-air mixture. When the throttle valve is in a more open position than the fast idle or second position shown in phantom designated position y in FIGURE 3, engine vacuum is blocked from outlet 100 but communicated to outlet 104, and the power by-pass valve is closed. Finally, when the throttle valve is substantially wide open,

engine pressure is sufliciently low to open the power bypass valve 59 and supply power enrichment in the conventional manner. The outlet 1% and conduit 106 have a smaller capacity than the outlet 1% and the chamber or conduit 102, The use of the combination of conduits 160 and 104 is operative to close the power by-pass valve at idle. This closing of the power by-pass valve at idle re duces the stalling frequency on both forward and backward stops because the fuel level in the main discharge jet system is lower when the power hy-pass valve is closed at idle. The functional description of operation for the embodiment shown in FIGURES 2 and 3 which preceded is substantially identical for both embodiments. The combination of outlets 16-? and 164 is thus operative to maintain the power 'by-pass valve closed at idle, opened at fast idle, and closed above fast idle until power operation is reached.

FIGURE 4 shows the performance of an embodiment of the present invention in use on an automobile carburetor. The performance of a conventional carburetor modified only in accordance with the present invention is shown in operation at an engine temperature of minus 25 F. in curves 89 and 82. In FIGURE 4, the mixture ratio or fuel richness in pounds of fuel per pounds of air is shown on the vertical axis, and air flow in pounds per hour is plotted on the horizontal axis. Air flow in pounds per hour is substantially proportional to engine speed. Air flow of about 75 to 85 pounds per hour in the invention embodiment tested corresponds to the cold engine fast idle speed range. Air flow of 100 pounds per hour to about 300 pounds per hour corresponds to the low and lowmedium speed range for the engine tested using an embodi ment of the present invention.

According to the present invention, after the engine starts, the throttle valve 76 is in the cold engine fast'idle position, shown in solid line in FIGURE 2, blocking vacuum from the duct outlet 68 which opens the power bypass valve 58 and enriches the mixture. Curve 80 represents a fuel-air mixture curve for a conventional automatic choke type carburetor having a fuel-air mixture of desired richness in the fast idle air flow region at a temperature equivalent to minus 25 F. Curve 82 represents a fuel-air curve for a similar carburetor operating under similar conditions having a more wide open vacuum kick position. The curve 82 is representative of engine requirements in the 200 to 600 pounds per hour air flow which corresponds to the low, medium and medium to high speed range for the vehicle which would use the carburetor, The fast idle area of curve 52, shown generally by numeral 88, is insufficiently rich for satisfactory engine operation.

Satisfactory operation may be achieved, however, by causing the power by-pass jet or valve 50 to open at the fast idle speed range. This is achieved by using the vacuum channel 66 which has an end opening in the induction passage 13 on the upstream side of the throttle valve 76 when it is in its fast idle position. The curve segment fit is representative of the fuel-air curve that is obtained with n this arrangement. Note that in the fast idle air flow range, the curve is identical or substantially so to thatof the curve 80 as the throttle valve is opened beyond its fast' idle position, the channel 66 is exposed to manifold vacuum which is operative to close the power by-pass valve 50, and to lean out the fuel-air mixture. This operation is shown in the range of curve segment 99 between the curves. 80 and 82. At the intersection of curve segment 9% with curve 82 which is at about the 200 pounds per hour air flow rate, the carburetor fuel-air mixture has leaned out to the desired point and the desirable leaner warm-up fuel-air curve is achieved.

The range of operation of the power bypass valve 59 may be controlled by modification of the channel size, the channel location, the throttle valve angle and the thickness of the throttle valve at the channel outlet.

It can be readily seen that the present invention achieves the stated objects. The mixture ratio curve at the test temperature does not exceed the cold engine idle range richness, and is considerably leaner than the conventional choke carburetor mixture ratio curve which does not employ the present invention. Thecold engine mixture ratio curve, for a prescribed fast idle mixture, is substantially leaner than the conventional choke mixtures during the driving operations that are slightly above the cold fast idle enginespeeds when the present invention is employed.

The present invention leans out the fuelair mixture at engine speeds above the cold engine idle range of about '75 to 85 pounds per hour. Prior art automatic choke carburetors enriched the fuel-air mixture at engine speeds above cold engine fast idle speed untfl the upper medium speed range was achieved.

In addition, the present invention does not interfere with the operation of the power by-pass valve at high engine speeds or high engine power.

Although only two embodiments of the present invention have been illustrated in the accompanying figures, and described in the foregoing specification, it is to be especially understood that various changes may be made to the embodiment shown and described without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art.

We claim:

1. In a carburetor for an internal combustion engine comprising:

a fuel-air induction passage;

a throttle valve mounted in said induction passage,

said throttle valve having a first normal idle open position and a second cold idle position of greater opening than said first position;

a choke valve mounted in said passage upstream of said throttle valve;

a fuel chamber;

a primary fuel system having a venturi disposed in said induction passage intermediate choke and throttle valves and fuel passage means supplying fuel from said fuel chamber to said venturi in response to the air flow through the venturi, said fuel passage means including a main metering jet therein;

by-pass valve means interconnecting said fuel passage means and said fuel chamber by-passing said main metering jet to provide an augmented supply of fuel when open;

a vacuum motor connected to said by-pass valve means to control its opening and closing in response to sensed vacuum; and

vacuum channel means connected to said vacuum motor having an outlet opening into said induction passage, said outlet located immediately upstream of said throttle valve when in said second position, thereby sensing a low vacuum operative to open said by-pass valve and provide augmented fuel during cold idle operation in cooperation with additional enrichment provided by said choke valve, said outlet operative to sense vacuum on the downstream side of said throttle valve for more open throttle valve positions and thereby control said by-pass valve in response to vacuum conditions prevailing downstream of the throttle valve for all positions substantially more Wide open than the cold idle position.

2. The apparatus as claimed in claim 1 wherein:

said vacuum channel means includes an additional outlet opening into said induction passage downstream of said throttle valve, when in said first position, and upstream of said throttle valve, when opened to said second position.

3. The device claimed in claim 2 wherein:

said additional outlet has a larger flow capacity than said outlet.

4. The device claimed in claim 2 including:

check valve means operative with said additional outlet to block flow therethrough when pressure at said additional outlet exceeds that at said outlet.

References Cited UNITED STATES PATENTS 1,798,388 3/1931 Westcott 261-69 X 2,038,206 4/1936 Chandler 261--69 X 2,404,645 7/1946 Mallory 26169 X 2,447,264 8/1948 Beardsley 26169 X 2,615,695 10/1952 Winkler 261--69 X 3,065,957 11/1962 Phillips 261-69 X 3,076,639 2/1963 Szwargulski et a1. 26169 X 3,181,843 5/1965 Brown et a1. 261-69 X HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Assistant Examiner. 

